Byline: David John Bailey Keywords: free-standing birth centers; place of birth; pregnancy outcome Abstract Background This study investigates maternal and perinatal outcomes for women with low-risk pregnancies laboring in free-standing birth centers compared with laboring in a hospital maternity unit in a large New Zealand health district. Methods The study used observational data from 47 381 births to women with low-risk pregnancies in South Auckland maternity facilities 2003-2010. Adjusted odds ratios with 95% confidence intervals were calculated for instrumental delivery, cesarean section, blood transfusion, neonatal unit admission, and perinatal mortality. Results Labor in birth centers was associated with significantly lower rates of instrumental delivery, cesarean section and blood transfusion compared with labor in hospital. Neonatal unit admission rates were lower for infants of nulliparous women laboring in birth centers. Intrapartum and neonatal mortality rates for birth centers were low and were not significantly different from the hospital population. Transfers to hospital for labor and postnatal complications occurred in 39% of nulliparous and 9% of multiparous labors. Risk factors identified for transfer were nulliparity, advanced maternal age, and prolonged pregnancy a[yen]41 weeks' gestation. Conclusions Labor in South Auckland free-standing birth centers was associated with significantly lower maternal intervention and complication rates than labor in the hospital maternity unit and was not associated with increased perinatal morbidity.